With the engine warm and the heat turned on, feel the hoses going through the firewall to the heater core. If one is hot and the other cold, you have a clogged heater core which must be backflushed to clear a blockage.

If the hoses are both cold, move up the hoses until you find a valve. This is the heater control valve. If it is hot on one side of the valve, that valve is clogged or shut. Investigate why the valve is not passing coolant - a clog or the actuator is broken/disconnected.

If both sides of the heater control valve are cold, replace the thermostat. While you have the thermostat housing open, make sure there are no blockages in the connection pipes.

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hope it helps

It is most probably the problem with blend door or blend door actuator. But just in case I would suggest to follow the entire procedure:

First you have to identify what causes the problem.
To do this you have to:1)When engine is cold check the level of coolant. If it is low fill it up.2)Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced3)If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.4)If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator. 5)If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

will the air flow switch from floor to the mid to defrost? if so then we have a problem with the tempature door actuator. easy to replace just in tight place. Keep me posted for more help or if this was any help thanks

Sounds like the air "blend" door might be inoperable. This door opens and closes a specified amount to regulate the amount of either cooled or heated air, as requested by the climate control unit. If the door is continually in the position which is bypassing the heater core (cold setting), the air will not get warm regardless of the condition/operation of the heater core. I'd suggest having this component checked.